1. A new cannulation technique was used to obtain soluble proteins of monkey interphotoreceptor matrix (IPM). The 7S interphotoreceptor retinolbinding protein (IRBP) was the major soluble protein of monkey IPM. There was no detectable cellular retinol-binding protein (CRBP) or cellular retinalbinding protein (CRALBP). Monkey IRBP is a glycoprotein of 146K molecular weight on SDS polyacrylamide gel electrophoresis and a native molecular weight of 250K on high-performance size-exclusion liquid chromatography. IRBP is synthesized by whole retinas in organ culture and secreted into the culture medium. 2. A soluble cGMP phosphodiesterase of 42K molecular weight on SDS-polyacrylamide gel electrophoresis and native molecular weight of 350K on high performance size-exclusion liquid chromatography was found in bovine and monkey IPM obtained by gentle washing of whole retinas in the light. 3. Binding of radiolabled retinol to CRBP was very low at early stages of corneal development in the chicken embryo. There was a several-fold increase in such binding at the pivotal 14th day of incubation when the initial increase in corneal transparency takes place.